The present invention relates to the production of the silyl maleates and more particularly the present invention relates to a novel process for maximizing the yield of the production of silyl maleates, fumarates, succinates and phthalates.
Silyl maleates are well-known, for instance, see the disclosure of U.S. Pat. No. 3,759,968 which is hereby incorporated by reference, with respect to silyl maleates also seen in the disclosure of French Pat. No. 1,337,516, U.S. Pat. No. 3,179,612 and British Pat. No. 1,099,619. When such silyl maleates were first developed, they were disclosed as being utilized as self-bonding additives for heat curable silicone rubber compositions. In a later patent application which is still pending, silyl maleates, fumarates, and succinates are disclosed as self-bonding additives for incorporation into one component room temperature vulcanizable silicone rubber compositions. Silyl phthalates were not disclosed in that patent application, which is Ser. No. 52,042, Smith et al, entitled "Shelf-Stable One Part Room Temperature Vulcanizable Silicone Rubber Compositions" filed Feb. 28, 1979. Although silyl phthalates were not disclosed in that patent application for use as self-bonding additives, they do have some utility as self-bonding additives for heat vulcanizable silicone rubber compositions. However, there was some difficulty with the process for the production of such silyl maleates, fumarates, succinates and phthalates (hereinafter, while reference is made to silyl maleates, it is understood that the same process conditions apply to the fumarates, succinates, and phthalates).
Accordingly, the processes that were disclosed in, for instance, U.S. Pat. No. 3,773,817 and related patents on the production of silyl maleates, fumarates, and other related compounds were not altogether advantageous. The difficulties of such processes will be disclosed below but to state matters simply the overall yield from such a process did not exceed 60 percent most of the time and many times the overall yield was considerably lower. There were two alternate processes of the prior art such as disclosed in the foregoing Berger et. al. U.S. Pat. No. 3,773,817 which was disclosed for the production of silyl maleates. One process was the taking of trimethoxyhydrogenosilane and reacting with the olefinic maleate. The disadvantage of this process was that hydrogenotrimethoxysilane is very hard to handle since it is dangerous material that can cause eye damage. In addition, the reaction is exothermic and difficult to control. In another aspect, the trimethoxyhydrogenosilane is the product of alkoxylating hydrogenotrichlorosilane which in itself is a difficult process for the reason that will be set forth below. Accordingly, a more acceptable process from the material handling point of view to react the olefin maleate with trichlorosilane in the presence of a platinum catalyst to produce trichlorosilylpropylmaleate. The resulting maleate was alkoxylated by reacting the trichlorosilylmaleate with methanol in the presence of an aromatic solvent at the temperature of 25.degree. to 70.degree. C. as disclosed in the foregoing U.S. Pat. No. 3,773,817.
The difficulty with such a reaction was that the methanol reacts with hydrogen chloride that is formed to produce methyl chloride and water. This is a competing reaction which tends to predominate and accordingly, the desired yield of a methoxylated product would be quite small. An undesirably side reaction would be that if the methyloxylation of the trichlorosilylpropylmealeates continues the alcohol and would react with a methoxysilylpropyl maleates in the presence of hydrogen chloride to cleave the trimethoxysilylpropyl ester group and yield a methoxy maleate ester. Both of these reactions as can be appreciated would give the desired yield of a methoxylated silylpropylmaleate compound. Accordingly, this methoxylation was hard to control and high yields were difficult to obtain utilizing the technique set forth in U.S. Pat. No. 3,773,817 and elsewhere.
Another alternative process was to use trimethylorthoformate to carry out methoxylation of bis-(trichlorosilylpropyl) maleate. However, the cost of this process is prohibitive such as to make it disadvantageous to use even though the proces operates properly and results in a high yield of product. It takes 6 moles of the trimethylorthoformate for one mole of a maleate to produce the desired methoxylated product. Accordingly, in spite of the fact that this process with trimethylorthoformate is desirable in that it results in a high yield of product with a minimum of side reaction, nevertheless, it is prohibitively expensive. Accordingly, it was highly desirable to find an inexpensive route for the production of methoxylated silylpropylmaleates fumarates, succinates, and phthalates. This was true whether there was one methoxy per silicon atoms in the maleate or three methoxy groups per silicone atom in the maleate, fumarate, succinate, phthalate.
Accordingly, it is one object of the present invention to provide an economical process for producing alkoxylated silyl maleates, fumarates, succinates, and phthalates.
It is an additional object of the present invention to provide an efficient and economic process for the production of alkoxylated silyl maleates, fumarates, succinates, and phthalates in over 75% yield.
It is an additional object of the present invention to provide a safe process for the production of alkoxylated silyl maleates, fumarates, succinates, and phthalates which does not result in the handling of hazardous or dangerous materials.
It is still an additional object of the present invention to provide a process for the production of alkoxylated silylmaleates, fumarates, succinates, and phthalates.
The process is carried out such that the entire addition reaction as well as the alkoxylation reaction takes place in one reaction chamber which results in an economical utilization of process conditions and process materials. These and other objects of the present invention are accomplished by means of a disclosure set forth herein and below.